It is well-known in the art of media broadcasting that various signal transmission formats may be used to broadcast signals. For example, some satellite television broadcasters transmit digital television signals using the Digital Satellite System (DSS) format, while others transmit digital television signals using the Digital Video Broadcast (DVB-S) format. A signal that is transmitted using a particular format is typically decoded by a set-top box that is configured to decode that format. In many cases this configuration is implemented at the hardware level, making it difficult or impossible to change the existing set-top box to accommodate different formats. Transmission formats may differ in several ways, such as their packet size, with DSS using smaller packets than DVB-S, and in the scrambling algorithm they use, with DSS using the Data Encryption Standard (DES) while DVB-S uses the DVB Common Scrambling Algorithm.
In some regions of the world broadcasters transmit content using multiple transmission formats simultaneously in order to serve customers with different types of set-top boxes. Not only is this an inefficient use of bandwidth, but it also very costly to do so rather to switch to a single transmission format and replace a large installed base of incompatible set-top boxes with compatible devices.
DVB-S, referred to above, is a published standard whose details are well-known in the art; see, for example, www.dvb.org. Some of the key standards include ETS 300 468 and ETR 162.
Conditional Access as a means of controlling access to broadcast items is well-known in the art. References on Conditional Access include the following:
1. “Functional Model of a Conditional Access System”, EBU Review-Technical, no. 266, Dec. 21, 1995, pages 64-77, Grand-Saconnex, Switzerland.
2. NDS Guide to Conditional Access, August 2000, available from NDS Limited, One London Road, Staines, Middlesex, UK.